Technical TECH WEEK: Cutting curved laminated glass the cheap and easy way.

I recently chopped my 51 chevy and couldnt really find anyone near me that would cut the windshield glass, all the local glass guys said it was a big deal to cut curved glass.

I did a little bit of research and some experimenting with a couple different ways and found it to be pretty easy and risk free to cut using a sand blaster...

All you'll need is a small sand blaster (I used one with a 1/4" nozzle) some good quality masking tape (I like the green scotch brand tape) some paint thinner or alike and some patience.

Im not very good at explaining things and I forgot to take pictures of the actual cuts I did on my windshield but iv got pictures of a practice cut I did on a spare chevy windscreen I had that worked out well so I will use those and try my best to explain how I did it (pretty straight forward)

basically all I did was mask a 1/8" line (both sides) in the glass where I wanted the cut layering the tape about 3 or 4 times so that it was thick enough to hold up to the sand blaster:

in this picture I already started blasting but you can see the tape and the paper protecting the rest of the glass.



I then slowly blasted away at the line back and forth (trying not to heat up the glass to much) until I got down to the laminate in the center then flipped it over and did the same on the other side...





I found that the laminate was really tough and wouldn't cut very well with the sand blaster so I poured some paint thinner down the cut line and it began to get soft pretty quick, I lit the thinners and the two pieces separated easily..







I used some 36 grit sand paper to sand the cut line smooth and I was done!

when I cut down my actual windshield the cut curved around but its exactly the same process, each piece of the windscreen only took me about an hour each to do.


Sooo yeah..... any questions?

 

Thanks for posting. Glad to see it works so well.

 

I have used this method before. works great. Slow and messy but but the results were worth it.

 

what about using a glass cutting tool, score both sides then BBQ fluid over the score, light it and it will melt through?

 

In theory it might work, but the results might not be what you are expecting. If it were that easy, more glass shops wouldn't hesitate to chop your windshield.

 

4rod- that-s how we used to do it at the glass shop I worked at. I like the sandblast idea too though.

 

Interesting. Best grit size? Pressure? Gary

 

I went to several glass shops that supposedly could cut windshields and none of them seemed the slight bit confident in their ability. At 2 or 3 hundred per windshield I dident feel confident trusting any of them. After a little research I decided that I could sandblast my own and make it on the first try. And I did. I used duct tape instead of masking tape (seemed the most resistant to the blast) with quite fine grit media and low pressure in a small cheapo blaster to slowly cut through. You can cut around corners just as easy as a straight line.

 

I did try that on a test piece but couldn't get it to work....

 

sorry I am unsure of the grit size although it was pretty coarse. and just normal shop compressor pressure, about 90 psi....

 

From experience, I can tell you make sure you use several layers of duct tape instead of that green tape. It doesn't take a whole lot to cut through that masking tape. Also, ALWAYS cover both sides of the glass completely if you are doing it for real. Otherwise, you will have little ricochet pieces of sand making little marks on the glass in areas you didn't think was possible. I usually use at least three layers of duct tape around the immediate area that I will be cutting, and then I use cardboard over the rest of the area that I want to protect. Once you get down to the plastic laminate in the middle, a simple box cutter will take care of that. No need for thinners or fuels that can wick their way into the laminate and cause damage.

 

What media did you use?
I ask because people talk about sandblasting even when they use glass beads, nutshell, aluminum oxide and well sand...

 

just normal sandblasting garnet.

 

thanks for the tip dude! Il use that next time!

 

My understanding was that the burning of the plastic was to assure the seal of the glass edges to the center core.

I don't know if this is true and I have never done it. Just trying to prod an explanation from someone in the know.

 

x2 on that. Even the "dust" from blasting will quickly frost the glass, and you can't polish that off. You won't even notice until the first time you drive into the setting sun. Trust me on that…
[
Brian

QUOTE=carlisle1926;9557037]From experience, I can tell you make sure you use several layers of duct tape instead of that green tape. It doesn't take a whole lot to cut through that masking tape. Also, ALWAYS cover both sides of the glass completely if you are doing it for real. Otherwise, you will have little ricochet pieces of sand making little marks on the glass in areas you didn't think was possible. I usually use at least three layers of duct tape around the immediate area that I will be cutting, and then I use cardboard over the rest of the area that I want to protect. Once you get down to the plastic laminate in the middle, a simple box cutter will take care of that. No need for thinners or fuels that can wick their way into the laminate and cause damage.[/QUOTE]

 

I have seen some work from a local blaster that has done both rock and wood signs and he says that he used rubber backed tape of some type, where he gets it I dont know. I would think finer grit would work best, and yes cover the whole window as suggested...thanks for he tech.

 

Rubber resist tape works best, at least at the cut line...used in the "tombstone" engraving biz!

 

haven't seen it done this way !

 

Cause hes showing another way to do it... Theres more than one way to skin a cat...

 

Curved glass doesn't like to be cut with tools made for flat glass!

 

blasting stencil made by anchor products . also you can use chuncks of old tape measure to cut the laminate. it is thin and flexible

 

http://intertapepolymer.com/Products/Industrial/Type/StencilProducts/Pages/default.aspx

I did a thread on this years ago but I didn't have curved donor to practice on . I was worried about the weight of the waste piece cracking the w/s when half done.

 

Think supporting it would help?

 

you can use three layers of 7mil duct tape it works great and sticks good.

 

After being cut and installed how does the glass hold up as far as delamation ?..I've had new glass [from two different places] that lasted only a year and it was just flat glass..

 

Havent had mine in for very long... so I couldn't tell you. Will let you know in a few years....

 

I chopped the windshield in my 55 Olds, back in 1984, and it still looks good, no delamination, but it's stored inside, though it did spend a years out of doors.

 

Good thread,,don't usually learn something new before my first coffee. How was the fit? I have made curved windshields for boats out of lexan and 2 cuts usually turned into a dozen for a perfect fit

 

Fit was pretty good I made templatea out of plexiglass first and test fitted them in the rubber which helped a heap the first time I did it I did it ofd mesurments and had to do 4 or 5 cuts before it fit and then I ended up breaking it putting it in cause it was to tight...